Arduino Uno brown-out level too low?

Someone on IRC just pointed out that the brown-out level of the Arduino Uno, at least the one specified by the [0xFD extended fuse in the boards.txt](https://github.com/arduino/ArduinoCore-avr/blob/master/boards.txt#L69) (not sure about manufactured boards) is 2.7V. Given that a 328 needs 3.6V to guarantee working at 16Mhz, this 2.7V sounds way too low. I double-checked the datasheet - an extended fuse of 0x04 would be better, which is a bod level of 4.3V (one step up).